The present invention relates to a system for transferring a fine pattern onto a target and, more particularly, to an X-ray lithography system for transferring a fine pattern to a target, for example a Si wafer, with X-rays.
Recently, X-ray lithography systems have been developed as lithography systems which are capable of improving the resolution of the pattern transferred to a target. The conventional X-ray lithography system is described in IEDM Technical Abstract, 1980, p. 415 to p. 419, Warren D. Grobman, "Status of X-ray Lithography". In this conventional X-ray lithography system, X-rays emitted from an X-ray source are projected on a wafer having an X-ray resist layer through a mask on which is formed a predetermined pattern to be transferred from an X-ray absorber, so that the predetermined pattern is transferred to the wafer.
It is known that the conventional X-ray lithography systems have the problems to be described below. The substrate for the mask is required to be transparent to X-rays. In order to satisfy this requirement, the substrate must be formed to have a thickness of only several microns or less. It is difficult to manufacture such a thin substrate from the viewpoint of manufacturing precision. Since the X-ray source can not be considered as a point source in a rigorous definition and the X-rays diverge with a relatively large divergence angle, it is required to arrange the mask and the wafer must be as close as possible to form a transferred pattern of satisfactory resolution on the wafer. In the actual systems, the mask is in contact with the wafer. Therefore, since the substrate of the mask is very thin, the mask may be damaged.